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What is Injection Blow Molding Machine?
A plastics injection blow molding machinery can be defined by understanding what injection blow molding is.
The injection blow molding machine's job is doing the injection blow molding in the process whereby the plastic preform is injection molded and the preform travels on the core rod to the blow mold station, where blow air enters through the core rod and lifts the hot preform material off the core rod and forms it by air pressure to the design of the female blow mold.
The injection blow molding machine's job is doing the injection blow molding in the process whereby the plastic preform is injection molded and the preform travels on the core rod to the blow mold station, where blow air enters through the core rod and lifts the hot preform material off the core rod and forms it by air pressure to the design of the female blow mold.
Injection blow moulding (IBM) is similar to extrusion blow moulding, except that the parison is formed by an injection molding process around a core rod or metal shank as shown in position 1 in the schematic in Fig. 3.29. The parison consists of a fully formed bottle/jar neck with a thick tube of polymer attached, which will form the body of the bottle. The parison/core rod is transferred into the blow molding part of the part of the machine at position 2 in Fig. 3.30. AT this point the preform is inflated and cooled. When cool enough the formed bottle rotates and the mold opens at position 3 and the bottle is ejected. There are three sets of core rods, which allow concurrent preform injection, blow molding, and ejection. This is the least-used of the three blow moulding processes, and is typically used to make small medical, cosmetic, and other single serve bottles.
Plastics Injection blow moulding is a combination process. First, we have to injection mould a preform and then blow it into the shape required, thus two moulds are required: one for the preform and one for the final blown form. The following methods can be used for producing blown mouldings from an injection moulded perform.
The two-stage blow moulding process is used for standard and stretch blow moulded items (Fig. 14.38). The preform is injection moulded as a separate stage, in a separate machine. The preform is designed to have a profile and variable wall thickness to provide the correct mechanical and barrier properties in the final blown moulding. Once moulded, the preform is reheated (different zones of the preform are heated to different temperatures to best suit the final blown form requirement) and placed in the blow mould. Air is introduced via the preform neck and the preform is blown into the shape of the mould. Venting is necessary so that all trapped air is removed from between the moulding and the mould. The mould has cooling ducts incorporated into its design. The coolant is usually water maintained at a constant temperature. To produce bottles suitable for carbonated beverages, the gas barrier and mechanical properties (tensile and burst strength) of the final bottle have to be greater than for a non-carbonated product not requiring a gas barrier.
The two-stage blow moulding process is used for standard and stretch blow moulded items (Fig. 14.38). The preform is injection moulded as a separate stage, in a separate machine. The preform is designed to have a profile and variable wall thickness to provide the correct mechanical and barrier properties in the final blown moulding. Once moulded, the preform is reheated (different zones of the preform are heated to different temperatures to best suit the final blown form requirement) and placed in the blow mould. Air is introduced via the preform neck and the preform is blown into the shape of the mould. Venting is necessary so that all trapped air is removed from between the moulding and the mould. The mould has cooling ducts incorporated into its design. The coolant is usually water maintained at a constant temperature. To produce bottles suitable for carbonated beverages, the gas barrier and mechanical properties (tensile and burst strength) of the final bottle have to be greater than for a non-carbonated product not requiring a gas barrier.
Stretch blow moulding can be carried out on both injection and extrusion processes (Fig. 14.39). In injection (the most common use) stretch blow moulding, the preheated preform held on the stretch rod is placed in the blow mould. Both the rod and the preform are heated to a controlled constant temperature, usually just above the Tg of the polymer, the bottle finish area being kept cool so that it does not distort. Once in the blow mould, the stretch rod pushes the preform to the bottom of the blow mould, air is introduced through the rod which expands the preform to the shape of the blow mould. In this way the material is orientated in both directions; this improves clarity, mechanical and barrier properties. Very lightweight bottles with good moisture and carbon dioxide barrier and pressure resistance properties can be produced using this method. Improved oxygen barrier can be obtained by using barrier materials such as polyamides and polyvinyl alcohol, the former can be added as a monolayer, but usually the barrier (oxygen scavenger) is added as a separate layer in the centre of the preform.
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